Process of treating synthetic lubricating oils with urea



United States Patent Office ?atente'd Jain. 5,1965

\ 3,164,555 PRGKIESS F TREATING SYNTHETIC I LUBRECATING GILS WITH UREA Rdbert A. 'Cupper, Ridgefieid, Co 'nn and Carl A.

Wolf, 'Jr., New York, N.Y.,'assignors to Union Carbide Corperation, a corporation of New York No Drawing. Filed Dec. 16, N60, Ser. No. 76,118

' 17 Claims. (Ql. 252-515) This invention relates to lubricating oil compositions of good viscosity and anti-sludging characteristics, and more particularly, to the improvement of providing lubricating oil compositions having improved anti-corrosive action on metals.

A wide variety of ester type synthetic lubricants are known in the art as being useful as lubricants for aircraft turbine engines havinghigh compression ratios and increased power outputs, such as turbojets and turboprop combustion engines. The use of synthetic esters has made it possible to extend the range of ambient temperatures encountered and allow increased engine operating temperatures.

However, the synthetic esters commonly employed as lubricants sufle'r from the disadvantage of being corrosive towards metal, particularly at high temperatures. It is immediately apparent that much damage can occur to vital parts of an engine by the use of lubricants which have corrosive action towards metal.

Accordingly, it is the object of this invention to provide lubricating oil compositions olfering increased corrosion protection towards metal.

It has now been found that the anti-corrosion characteristics of synthetic esters can be markedly improved by treating said esters with urea.

The novel lubricants of this invention are "prepared by adding from 0.05 to 1.0 percent by weight'of urea to a base fluid, or mixtures of base fluids, and heating to a temperature within the range of 125 to 250 C, The preferred temperature range is from 180 to 210 C. and the preferred concentration of urea is 0.1 to 0.5 percent by weight. r

If the base fluid being treated has a tendency to decompose, it is preferred to conduct the heating at reduced pressures or under an inert atmosphere or under both an inert atmosphere and reduced pressure.

The term base fluid, as used in the specification and the claims, refers to synthetic esters including diesters, polyesters and polyglycol derivatives, which are used as bases for lubricants.

After the base fluids have been heated for a period of time, which varies with the particular base fluid, but is usually from to 60 minutes, they are subjected to a conventional filtration step to remove precipitated materials.

The synthetic base fluids to which the urea is added are well known in the art. It is to be understood that the novel lubricants of this invention contain a base fluid or mixtures of base fluids which are conventional. The instant invention does not reside in the particular base fluids but rather in the treatment of conventional base fluids with urea to obtain lubricants having superior anti-corrosive action on metals, particularly copper and lead.

The base fluids which can be treated with urea include:

(A) Diesters of aliphatic dicarboxylic acids which cor respond to the formula:

wherein n is an integer from 2 to 18, each R represents alkyl or cycloalkyl radicals having from about 5 to 24 carbon atoms and preferably from about 5 to 18 carhen atoms, and R represents hydrogen or alkyl groups having from 1 to 4 carbon atoms. The dicarboxylic acids may be substituted, such as, for example, 3-methy1 glutaric acid, to obtain lower viscosities at low temperatures so long as this substitution is consistent with the need for obtaining a low freezing point. Specific examples of organic dicarboxylic acids from which the esters may be derived are suberic, adipic, brassilic, iapanic, sebacic, glutaric, azelaic, and pimelic acids, as well as mixtures of these acids. The preferred acids are azelaic, adipic, and sebacic acids.

The alcohols used to form the diester of the acid may be branched chain or straight chain, saturated or unsaturated, aliphatic or cycloaliphatic alcohols. Typical alcohols which may be employed include 2-ethylhexyl alcohol, isooctyl alcohol, isodecyl alcohol, 2-ethylbutyl alcohol, cetyl alcohol, n-octyl alcohol, amyl alcohol, oleyl alcohol, Z-butyloctyl alcohol, methyl and dimethylcyclohexanol, and the 0x0 alcohols, such as the mixed branched chain nonanols, prepared from the reaction of carbon monoxide and hydrogen upon olefins which normally have a branched chain structure. Mixtures of alcohols can also be used such as a mixture of Z-ethylhexyl and isodecyl alcohol.

Representative synthetic diester lubricants which can be employed in conjunction with this invention include di-(2-ethy1hexyl)sebacate,

di- (2-ethylhexyl) azelate,

di [mixed- (Z-ethylhexyl, isodecyl) azelate, di- (isooctyl azelate,

di- 1-methylcyclohexylmethyl) seb acate, di- Z-ethylhexyl, decyl) azelate,

di- (2-ethylhexyl-Z-propylheptyl) azelate, di- (2,2,4-trimethylpentyl sebacate,

di- Z-methylpentyl, decyl) azelate, di-(1-ethyipropyl)adipate,

di- (3 -methylbutyl) adipate,

di 1 ,S-dimethylbutyl) adipate,

di- 2-ethylbutyl adipate,

di- (Z-ethylhexyl) adipate,

di- (isooctyl) adipate,

di- (undecyl adip ate,

di- (tetradecyl adipate,

di- (heptadecyl) adipate, di-(2,2,4-trimethy1pentyl) adipate,

di-( l-methylcyclohexylmethyl) adipate, dil-ethylpropyl) -azelate,

di- 3 -methylbutyl) azelate,

di- 2-ethylbutyl azelate,

dil-ethylpropyl) seb acate,

di- 3-methylbutyl) sebacate,

di- 1,3-dirnethylbutyl sebacate,

di- (Z-ethylbutyl) sebacate,

di- (Z-ethylhexyl) sebacate,

di- 2- (2-ethylbutoxy) ethyl) sebacate, di- (undecyl sebacate,

dif(tetradecyl sebacate,

di- (heptadecyl) sebacate,

di- Z-ethylhexyl) glutarate,

di- (undecyl) glutarate,

di- (tetradecyl) glutarate, and the like.

(B) Esters of aromatic acids which correspond to the general formula:

Z(COOR wherein Z represents a phenyl radical or a naphthyl radical, 12 represents an integer from 2-4 and R has the same meaning as previously described.

Examples of acids'from which the esters can be prepared include phthalic terephthalic, pyromellitic, naphthalene-1,4-dicarboxylic acid, etc. The alcohols which are reacted with the aromatic acids are the same as those mentioned under A.

(C) Complex glycolcentered esters having the general formula:

'wher ein n represents a number from 3-51, R represents alkyl or cycloalkyl radicals having from 4 to 24 carbon atoms and R represents hydrogen, methyl or ethyl.

' Examples of the above esters include 3-methyl-1,5-

pentanediol diisodecanoate and hexamethylene 1,6-glycoldiisooctanoate.

(D) Complex glycol centered esters containing recurring 'ether linkages represented by the formula:

wherein n is an integer from 3-4 and R represents an alkyl group having from 0-8 carbon atoms, with the proviso that when R is 0, n is 4, and m is an integer from O to 18.

Examples of alcohols which are reacted with aliphatic monocarboxylic acids include trimethylol ethane, trimethylol propane and pentaerythrytol.

It is to be understood that the above classes of base fluids are representative of art recognized fluids and are merely illustrative of some of the base fluids useful in this invention. The complex esters have been described in the art as well as in U.S. Patents 2,575,195; 2,575,196; and 2,703,811.

(F) Alkyl terminated polyesters: These are complex polyesters prepared from polyhydric alcohols and polybasic acids wherein reactive carboxyl or hydroxyl groups are terminated by reaction with either monofunctional alcohols or acids. These esters are known in the art and described in U.S. Patent 2,705,724. The disclosure of said patent is incorporated by reference into this application.

(G) Non-terminated or hydroxyl terminated polyesters: This class of compounds refers to those polyesters having free hydroxyl groups in the polymer chain which are not blocked or terminated by reaction with monofunctional or polyfunctional compounds. These compounds are known in the art and can be prepared by reacting a dibasic acid with a glycol or alkane diol as disclosed in U.S. Patent 2,929,786 or by reacting a dibasic acid with mixtures of polypropylene glycol and a 1,3-alkanediol as disclosed in copending application Serial No. 718,971.

(H) Polyalkylene glycol derivatives: These compounds can be represented by the formula:

114 R wherein R represents hydrogen or an alkyl radical having from 1-12 carbon atoms, R represents hydrogen or an alkyl radical having from 12 carbon atoms and each of n, m and X represent a positive integer from 1-25.

The integers m and n can be varied so as to provide homoand heteropolymers, i.e., polyoxyethylene glycols, polyoxypropylene glycols, mixed poly(oxyethylene-oxypropylene) glycols and also the monoand diethers of the above.

This class of compounds is well known in the art and the individual members of this class can be made in a variety of ways. Illustrative of the above class of compounds, as well as methods for the preparation of individual members are U.S. Patents 2,293,868; 2,425,755; 2,425,845; 2,448,664; 2,520,611 and 2,520,612.

The preferred compounds in this class are the monobutyl ethers.

It is to be understood that this invention relates to the treatment of base fluids in a novel manner and not to the particular base fluids employed. Thus, the above classes of base fluids (A to H) are representative of base fluids which can be treated according to the novel process of this invention. It is also within the scope of this invention to treat mixtures of base fluids which have been designated by A to H.

It is to be understood that the novel lubricants of this invention can contain conventional additives, e.g., viscosity index improvers, detergents and antioxidants, as is customary in this art. The preferred antioxidants are amine compounds such as phenothiazine, N-phenyl-betanaphthylamine, N-phenyl-alpha-naphthylamine, and phenolic compounds such as di-tert-butyl' para-cresol and butylated hydroxylanisole.

The following table depicts the critical specifications of a gas turbine lubricant and is based upon U.S. Specification Mil-L-7808C. Somewhat similar specifications are required for turboprop lubricants as described by EMS 35E of the Allison Division of General Motors Corporation and Specification D. Eng. RD. 2487 (Second Issue) of the British Ministry of Supply.

7 TABLE I.CRITIQAL GAS TURBINE AIRCRAFT LUBRI- CANT SPECIFICATIONS Corrosion and Oxidat on Standard 352 F. Test 347 I Test:

Weight Change, mg./sq. en1.:

Copper 510.4 :|=0. 4 Magnesium =l=0. 2 Aluminum =|;0. 2 Steel =|=0. 2 i0. 2 V Si1ver i=0. 2 Lead 5:1. 0 Viscosity Change, 100 F., percent 5 to +15 5 to +15 Neut. N0. Increase, mg. KOH/g 2.0 2.0

SOD lead corrosion, 1 hr. at; 325 F., 6.0 (max).

mgJsq. in. f Corrosion, 50 hr. at 450 F., mg./sq. in.

Copper 3.0 (max). Silver 3.0 (max). Panel coking, 8 hours at 600 F mg. (max) Test meth0ds.-The 352 Fgcorrosion and oxidation test was employed as the primary tool to evaluate ureatreated fluids. The 352 F. test, designed to simulate the standard military corrosion and oxidation test (79153084) was simplified by eliminating aluminum, magnesium, and silver metals, and adding a lead specimen. Steel and copper coupons are used in both tests. The 352 F. test consists of maintaining the test fluid at test temperature in the presence of the steel, copper, and lead specimens for 72 hours while purging with air at the,

- for viscosity change.

procedure employed by the military for evaluating the duced the lead corrosion rate from 11.5 milligrams per square inch to 0.19 milligram per square inch.

Example 3 A-- sample of tri-(Z-ethylhexyl) phosphate (Flexol TOP) was treated by adding 0.5 percent urea to the dried fluid and agitating at 160165 Rim 5 minutes. This fluid, as well as an untreated sample from the same batch, after addition of.0.5 percent phenothiazine, were exposed to the 352 F. corrosion and oxidationtest. 'Copper and lead corrosion rates are show nbelow.

tendency of gas turbine lubricants to corrode lead. .The Allison Division (General .Motors Corporation) aircraft gas turbine lubricant specifications include the SOD lead corrosion test. This test consists in rotating copper and lead (weighed) specimens for one hour in the test fluid which is maintained at 325 F. During the test, air is Weight Loss,mg /cm passed through the fluid at a rate of 57 liters per hour. The weight change of the lead specimen, in milligrams Copper Lead per square inch, is determined. At the present time, all r lubricant specifications containing this test allow a maxi- 1Z Iore rea t mer t-- 23.0 63.3 mum lead corrosion value of 6.0 milligrams per square er men TABLE IL-TREA'IlllENT OF ALIPHATIC DIBASIC ACID ESTERS WITH UREA [Antioxidant=0.5% (Wt.) purified phenothiazine] Base Fluid CB-ClO'AZ- Cs-Cro-Az. Cs-Cro-AZ. Cs-Cio-AZ. Gg-Cm-AZ. Ca-Ad 3 Ca-Ad Treatment 1 None 0.1% Urea 0.25% Urea 1.0% Urea 0.5% Urea None 0 5% Urea at 180 C. at 180 C. at 180 C. 195 205" O. 180 0 352 F. Corrosion-Oxidation:

Viseofsjity Change at 100 F., Per- +4.5 +4.7 +3.9.-. +3.5 '+1.9

Insolubles Formed Moderate Moderate Moderate Moderate Small 7 Appearance of Metals: V

Steel Brown-Bronze" Brown-Bronze Brown-Bronze Steel-Bronze Shmy-Gray Copper Dull Brown Dull Steel- Steel-Copper Steel-Copper" Dull, Red- Copper. Orange. Lead Gray-Black Dull Gray Dull Gray Dull Gray D%l11,(1 ray Steel +0.05 N1] Lead 0.ll +0.09. SOD Lead Corrosion, rug/in. -0.19 -115...

1 Treatment consisted in thoroughly mixing the urea with the base fluid with mechanical agitation and nitrogen purging ior'% hour at the temperature indicated.

2 Di-[mixed (Zethylhexyldsodeeyl)azelate]. 3 Di(2-ethylhexyl)adipate.

The following examples illustrate the novel lubricantsof this invention.

Example 1 A sample of refined di-(Z-ethylhexyl, isodecyl)azelate, containing 0.5 percent phenothiazine as an antioxidant, was tested in the 352 F. corrosion and oxidation test. The lead corrosion rate was found to be 1.6 milligrams per square centimeter. Separate portions of this diester were then treated with 0.1 to 0.25, and 1.0 percent urea at 180 C. Another portion was treated with 0.5 percent urea at 195-205 C. These treated samples were then tested in the 352 F. corrosion oxidation test after the addition of 0.5 percent phenothiazine. The data in Table II illustrate the marked decrease in the lead corrosion rate resulting from the urea treatment. .The optimum urea concentration'is about 10.5,percent. The untreated sample and a sample treated with 0.5 percent urea were also evaluated in-the SOD lead corrosion. test. Phenothiazine was again used as the antioxidant. Again a substantial reduction in the lead corrosion rate was observed (Table 11).

Example 2 Example 4 Di-(Z-ethylhexyl, isodecyl)azelate was prepared by tetrabutylorthotitanate catalysis as a residue product. p Be- Q tion of the crude diester was treated with 0.05 percent melaminebymixing for 15 minutes at 1109- C. and contact filtering with diatomaceous earth. Comparative results of the two treatments areshown below:

Weight change, mg/em.

Copper Lead Melamine Treated Nil 0. 11 Urea Treated +0.03 -0. 03

Example 5 A sample of polypropylene glycol 425 azelate was treated with ureaaccording to the procedures outlined in 'Table III. The 352 F. corrosion and oxidationtests [352 F. corrosion and oxidation tests.

TABLE III.TREAT MIENT OF POLYESTERS WITH UREA glycol 425 azelate, 0.5% Purified Phenothiazinc] Test fluid composition80.0% (wt.) di-(2-ethylhexyl, isodecyDazelate. 19.5% (Wt) 186-ll polypropylene Polypropylene Glycol 425 Azelate 186-11 1 186-11R-1 2 18611U.5 (120) 18611U.5 (180) 18611U.1 5 18611U.5

Viscosity Change at 100 +2.0 +2.2 +3.1 2.2 0.34 1.2.

F., Percent. Insoldbles Formed None None SmalL. Slight N Slight. Appearance of Metals:

Steel Brown-Bronze BrownBronze Brown-Bronze BrownBronzc Brown-Bronze Brown-Bronze.

Copper Pale, Pink- Bright, Light Brown-Copper Brown-Copper Steel-Copper Pale.

Copper. Copper.

Lead Gray-Black Gray-Black Brown-Gray Light Gray Blue-Gray Dull Gray. Metal Weight Change, mgJcmfi:

Step1 Nil Nil 0.019 Nil 0.013 +0.05.

Copper l 0.24 0.084 0.2l 0.273 -0.273 0.169.

Lead 1.45 1.1 0.47 0.06 0.05 -0.39.

d Polypropylene Glycol 425 Azelate prepared from a 1.18:1.0 mole ratio of Polypropylene Glycol 425 and Emery Industries Emcrox 1110 Azclaic am 2 R-1=treatment with 0.05% (Wt) melamine at 110-120 C.

3 Treated with 0.5 percent (Wt) urea for one-half hour at 120 C. 4 Treated with 0.5 percent (Wt) urea for one-half hour at 180 C. 5 Treated with 0.1 percent (Wt.) urea. for one-half hour at 240 C. 6 Treated with 0.5 percent (Wt.) urea for one-half hour at 240 C.

Example 6 A sample of polypropylene glycol 425 azelate was prepared by a conventional esterification procedure using tetrabutyl orthotitanate as the catalyst and xylene as the azeotroping diluent. At the completion of theesterification reaction separate samples of the crude product were treated with urea as shown in Table IV.

Example 8 Two blends composed of 59.5 weight percent of di-(Z- ethylhexyl isodecyl)azelate, weight percent Ucon 3O LB-625, and 0.5 weight percent N-phenyl-alpha-naphthylamine were evaluated in the SOD lead corrosion test. One blend contained the urea-treated Ucon LB-625 described in Example 7; the other was prepared from un- 7 TABLE IV.-TREATMEN Test fluid composition (percent by Weight):

80.0% di-(2-ethylhexyl, isodecyD-azelate. 19.5% 186 polypropylene glycol 425 azelate.

0.5% Purified phenothlazine.

T OF CRUDE POLYPROPYLENE GLYCOL 425 AZELATE WITH UREA Polypropylene Glycol 425 Azelate 352F. Corrosion-Oxidation:

Viscosity Change at 1.1 2.2 0.6.

100F., percent.

, Insolubles Forme Small. N n Small.

Appearance of Metals:

Steel Brown-Bronze. Brown-Bronze-.. Brown-Bronze.

Dull, Pale Dull Bright Gold Copper. Dull, Gray-Black.

' ene glycol monobutyl ether having a 100 F. SUS viscosity of 625) was treated by mixing thoroughly with 0.5 percent urea for one-half hour at 180 C. while purging with nitrogen. Samples of the treated and untreated fluid were tested in the SOD lead. corrosion cell. The untreated fluid exhibited a lead weight loss of 2.0 milligrams per square inch, whereas the urea-treated sample showed a weight loss of only 0.15 milligram per square inch. One percent N-phenyl-alpha-naphthylamine was used as the antioxidant in each of these fluids.

treated Ucon LB-625. In the case of the untreated sample, a lead weight loss of 15.5 milligrams per square inch was obtained whereas a weight loss of only 5. 6 milligrams per square inch was obtained for the treated sample.

Example 9 A lubricant blend composed of 81.0 weight percent of di-(Z-ethylhexyl, isodecyl)azelate, and 19.0 percent polypropylene glycol 42 5 azelate was treated by mixing thoroughly with 0.5 percent urea for one-half hour at about -190 C. This blend and a similar-blend, which was not treated, were tested by means of the 352 F. corrosion and oxidation test. Data showing the improvement in corrosion characteristics resulting from urea treatment are shown in Table V.

TABLE 'V.UREA TREATMENT OF. A DIES/PER- POLYESTER BLEND .Test' fluid composition:

99. -{Di-(2-ethylhexyl, isodecyD-azelate. 0. 5% I Polypropylene glycol 425 azelate. 0. 5% Purified Phenothiazine.

ing/in.

1 Treatedby mixing with 0. 5% urea for one-half hour at 180190 C. while purging with nitrogen.

and 31.9 milligrams per square inch respectively, when tested by the SOD lead corrosion procedure. After treatment of each of thesediesters with 0.25 percent by weight of urea at 200 6., they exhibited lead corrosion values of 1.07 milligramsper square inch for the diisooctyl adipate and"-0.54-milligram per square inch'for the diisodecyl adipate.

As is evident from the foregoing examples and tables, the novel lubricants of this invention possess superior anticorrosive properties.

What is claimed is:

l. A process which comprises contacting a synthetic lubricant base fluid with from 0.05. to 1.0 weight percent of urea, based on weight of said synthetic lubricant base fluid, at an elevated temperature, for a period of time sulficient to produce a synthetic lubricant having reduced corrosive tendencies to metals, said synthetic lubricant base fluid being of the group consisting of organic polyesters andorganic ethers which are composed only of carbon, hydrogen, and oxygen.

2. The process of claim 1 wherein said process is carried out at a temperature in the range of from 125 C. to 0" C.

TABLE VL-POLYOL CENTER ESTERS [Antiozidant0.5% purified phcnothiazine. 852 F. Corrosion Oxidation Test] Urea Treatment Metal Weight Change,

rug/cm. Viscosity Ester Urea Change Insolubles Cone, Temp., Tim at 100 F., Steel Copper Lead Wt. 0. Min. Percent Percent Diethylene Glycol Di-isodeeanoate None +108 Moderate-Large.-- +0.08 0. 26 154 Do 0.5 220 30 +6.2 Moderate +0.05 0.02 24.1

Example 10 3. The process of claim 2 wherein the synthetic lubri- (A) A sample of di-(isodecyl) adipate was treated with 0.1% by weight of urea at 200 C. for approximately /2 hour. The treatment was followed by contact filtration with diatomaceous earth to remove residues.

(B) A sample of di-(isooctyl) adipate was similarly treated.

(C) A sample of UCON Lubricant LB-1715 (a polyoxypropylene glycol monobutyl ether having a 100 F. SUS viscosity of 1715) was treated with 0.25% by Weight of urea at 180 C. for approximately thirty minutes. The treatment was followed by contact filtration with diatomaceous earth to remove residues.

(D) A mixture was prepared consisting of:

3 0% by weight of A 69% by weight of B 1% by weight of C The properties of this mixture are shown in Table VII and are contrasted with a mixture of the same components in the same proportions which have not been treated with urea.

TABLE VII.-ADIPATE DIESTER-POLYOXYPROPYL- ENE GLYCOLMONOBUTYL ETHER COMPOSITION [352 F. corrosion-oxidation test. Ant'iowidant-0.5%

Samples of commercial diisooctyl adipate and diisodecyl adipate were found to have lead corrosion values of 33.0

cant product is separated from solid material formed during said process.

4. A process for producing a synthetic lubricant which comprises the steps of contacting a synthetic lubricant base fluid with from 0.05 to 1.0 weight percent of urea, based on weight of said synthetic lubricant base fluid, at a temperature in the range of from C. to 250 C., for a period of from 10 to 60 minutes, and thereafter recovering the synthetic lubricant thus produced, said synthetic lubricant base fluid being of the group consisting of organic polyesters and organic ethers which are composed only of carbon, hydrogen, and oxygen.

5. A process which comprises contacting a dialkyl diester of an alkanedioic acid with from 0.05 to 1.0 weight percent of urea, based on weight of said diester, at a temperature in the range of from 125 C. to 250 C. for a period of from 10 to 60 minutes, and thereafter recovering the said diester having reduced corrosive tendencies to metals which is thus produced, wherein the alkyl moieties of said diester have from 5 to 24 carbon atoms, and wherein the said alkanedioic acid has from 2 to 18 carbon atoms. 7

6. A process which comprises contacting a fully esterified alkyl ester of an aromatic polycarboxylic acid having from 2 to 4 carboxylic acid groups, with from 0.05 to 1.0 weight percent of urea, based upon weight of said ester, at a temperature in the range of from 125 C. to 250 C. for a period of from 10 to 60 minutes, and thereafter recovering the said ester having reduced corrosive tendencies to metals which is thus produced, wherein the alkyl moieties of said ester have from 5 to 24 carbon atoms.

7. A process which comprises contacting a fully esterified alkanoic ester of an alkanepolyol with from 0.05 to 1.0 weight percent of urea, based on weight of said ester, at a temperature in the range of from 125 C. to 250 C. for a period of from 10 to 60 minutes, and thereafter recovering the said ester having reduced corrosive tendencies toward metals which is thus produced, wherein the alkanoic moieties of said ester have from to 25 carbon atoms and wherein said alkanepolyol has from 2 to 6 carbon atoms and from 2 to 4 alcoholic hydroxyl groups.

8. A process which comprises contacting a di'alkanoic diester of a polyoxyalkylene glycol with from 0.05 to 1.0 weight percent of urea, based on weight of said diester, at a temperature in the range of from 125 C. to 250 C. for a period of from to 60 minutes, and thereafter recoverting the said diester having reduced corrosive tendencies to metals thus produced, wherein the alkanoic moieties of said diester have from 5 to 25 carbon atoms and wherein the oxyalkylene moieties of said polyoxyalkylene glycol have from 2 to 3 carbon atoms.

9. A process which comprises contacting a monoalkyl ether of a polyoxyalkylene glycol with from 0.05 to 1.0

. weight percent of urea, based on weight of said ether, at a temperature of from 125 C. to 250 C. for a period of from 10 to 60 minutes, and thereafter recovering the said ether having reduced corrosive tendencies to metals thus produced, wherein the alkyl moiety of said ether has from 1 1 to 12 carbon atoms and wherein the oxyalkylene moieties of said ether have from 2 to 3 carbon atoms.

10. The process of claim 5 wherein said dialkyl diester of an alkanedioic acid is 2-ethylhexyl isodecyl azelate.

11. The process of claim 5 wherein said dialkyl diester of an alkanedioic acid is di(2-ethylhexyl) adipate.

References Cited in the file of this patent UNITED STATES PATENTS 2,224,158 Marks et al Dec. 10, 1940 2,408,090 Musher Sep. 24, 1946 2,599,736 Adelson et a1 June 10, 1952 2,657,984 Braithwaite et a1. Nov. 3, 1953 2,727,025 Weitkamp Dec. 13, 1955 2,908,647 Vaughn Oct. 13, 1959 2,929,786 Young et al Mar. 22, 1960 2,944,973 Langer et al -luly 12, 1960 3,044,949 Schlenk July 17, 1962 OTHER REFERENCES McTurk, Synthetic Lubricants, USAF Wright Air Development Center Technical Report 53-88 (Oct. 3 Printed by McGregor & Werner, Inc., Dayton, Ohio (March 1954). Pages 20-21, 33-34, 43-44 pertinent. 

1. A PROCESS WHICH COMPRISES CONTACTING A SYNTHETIC LUBRICANT BASE FLUID WITH FROM 0.05 TO 1.0 WEIGHT PERCENT OF UREA, BASED ON WEIGHT OF SAID SYNTHETIC LUBRICANT BASE FLUID, AT AN ELEVATED TEMPERATURE, FOR A PERIOD OF TIME SUFFICIENT TO PRODUCE A SYNTHETIC LUBICANT HAVING REDUCED CORROSIVE TENDENCIES TO METALS, SAID SYNTHTIC LUBRICANT BASE FLUID BEING OF THE GROUP CONSISTING OF ORGANIC POLYESTERS AND ORGANIC ETHERS WHICH ARE COMPOSED ONLY OF CARBON, HYDROGEN, AND OXYGEN. 